Aerogels are three-dimensional network of nanophase architecture composed of gas [usually air] and solid structure, with air [gas] to solid ratio of 60-98% by volume. Thus aerogels have high porosity, high specific surface area, and very low density. Aerogels can be made as large monolithic shapes, or micron/submicron size bodies, or any size and shape in between. The gas inside the aerogel nanostructures can be replaced [displaced] with other substances, such as, for example, pharmaceuticals, which then are released into the desired targets in a controlled manner. Further, incorporation of targeting proteins/agents, such as, for example, EGF [epidermal growth factors for cancer cells] into the aerogel structure and loading the aerogel nano-chambers [pores] with a medication, such as, for example, Paclitaxel or melittin, makes it possible to deliver the drug selectively and specifically to cancer tumors, rather than indiscriminately to all cells. Thus, only cancer cells would be destroyed without any significant side effects to healthy cells.
Aerogels made from PEG [polyethylene glycol] are non-toxic, biocompatible with “stealth” properties to prolong their stay in blood stream and biodegradable with no harmful side effects. This makes them an excellent choice for use in biomedical applications. Indeed, PEG is widely used in the pharmaceutical industry because of its non-toxic and non-immunogenic properties. In addition to its excellent tolerance in humans, PEG stabilizes the physiological function of proteins and bioactive substances. However, and unlike nanoparticles and other drug carriers, aerogels can contain much larger volumes of drugs inside their structure and, thus, the drugs are protected until they reach their intended targets.
Examples of the drugs that can benefit from encapsulation or incorporation in PEG aerogels include, for example, poorly water soluble drugs such as, for example: Paclitaxil, alprostadil, amphotericin B, camptothecin, cosalane, chloramphenicol, cyclosporine, iovastatin, omeprazole, dexamethasone, HIV-1 protease inhibitors, hydroxycortosone, indomethacin, phenytoin, and tolbutaide; and proteins of different sizes and stabilities, such as, for example, insulin-5700, IgG-150,000, and interferon.
Prior proposals in the field include U.S. Pat. Nos. 5,869,545, 6,475,516, 6,623,729, 6,703,047, 6,890,560, 6,994,842, 7,018,645, 7,135,190, 7,589,157, 7,648,713, 7,732,427, and 7,731,988; published applications 2009/0291115, 2010/0112057; EP No. 0130577 and 1019446; AUS 9,965,549 and 711,078; and Smirnova, et al., “Feasibilty of hydrophilic and hydrophobic silica aerogels as drug delivery systems”, Journal of Non-Crystalline Solids, 350 (2004) 54-60.